The effect of cobalt on the growth of young lucerne on a siliceous sand

Summary The nodulation and growth of young lucerne plants on a moderately acid siliceous sand were greatly increased by inoculation and the application of lime. In addition cobalt treatment significantly increased the yield of nitrogen per nodulated plant and the amount of nitrogen fixed per nodulated plant but had no effect on non-nodulated plants. Cobalt significantly increased the fresh weight of nodules per plant, due to greater nodule size. Furthermore the amount of nitrogen fixed per unit fresh weight of nodular tissue was substantially increased. The effects of cobalt on symbiotic nitrogen fixation led to significant increases (29 to 77 per cent) in the dry-matter yield of lucerne tops.